Remote control system for a multimedia scene

ABSTRACT

The invention relates to a control system for a multimedia scene defined by a scene description, said control system comprising a video receiver suitable for receiving the multimedia scene, and a remote control device provided with keys. The video receiver is intended to communicate with the remote control device. To this end, it comprises a user interface intended to identify a key of the remote control device when it is pressed and to associate said key with a key of a virtual keyboard defined in the scene description. It also comprises means intended to activate the key of the virtual keyboard and to execute a command associated with said key, said command being intended to modify a content of the multimedia scene.

The invention relates to a control system for a multimedia scene definedby a scene description, the control system comprising a video receiversuitable for receiving the multimedia scene.

It also relates to a method of controlling a multimedia scene defined bya scene description.

The invention notably finds its application in apparatuses which arecompatible with the MPEG4 standard or an equivalent standard by which auser can interact with the content of a multimedia scene.

The MPEG4 standard comprises tools allowing the composition of a set ofmultimedia objects such as, for example, a person, a background, a pieceof furniture or a voice, within a multimedia scene. The informationrequired for the composition of the scene forms a scene descriptionwhich is encoded and transmitted with the multimedia objects. The MPEG-4standard has developed a binary language for the scene description,referred to as BIFS format (Binary Format for Scene). In a generalmanner, the scene descriptions are encoded independently of thedifferent multimedia objects. These scene descriptions notably comprisethe parameters allowing modification of a multimedia object, forexample, its position in the scene.

An MPEG4 scene has a hierarchic structure which may be represented inthe form of a tree. Each node of this tree is a multimedia object. Thetree structure is not necessarily static; node attributes such asparameters for positioning the multimedia object may be modified, whilenodes may be added, replaced or removed in said tree structure.

In accordance with the MPEG-4 standard, the multimedia objects have atemporal and spatial dimension. Each multimedia object has its own localsystem of coordinates. This local system of coordinates allowsmanipulation of the multimedia objects both in space and in time. Themultimedia objects are positioned in a scene by virtue of a geometricaltransformation which is suitable for converting the coordinates of themultimedia object in the local system of coordinates into coordinates ina global system of coordinates defined by a parent node of the scenedescription in the tree.

The multimedia objects and the scene description n(

parameters for a composition layer through which their behavior such as,for example, the intensity of a sound or the color of a video object canbe controlled.

In order that a user can interact with the content of the multimediascene, the standards VRML97: ISO/IEC 14772-1: 1997 and MPEG-4 systems:ISO/IEC 14496-1 have created a specific node referred to as TouchSensornode. This node provides the possibility of following the position andthe state of a cursor device of the computer mouse type and of detectingwhen the user clicks with said cursor device in a zone comprising theTouchSensor node corresponding to a multimedia object selected in thescene.

However, the interactivity with an MPEG-4 scene is currently onlypossible with such a cursor device.

It is an object of the present invention to propose a system and amethod of controlling a multimedia scene defined by a scene descriptionallowing interaction with a multimedia scene by means of a remotecontrol device, i.e. without the use of a cursor device.

To this end, the video receiver included in the control system accordingto the invention is characterized in that it comprises a user interfaceintended to identify a key of the remote control device when it ispressed and to associate said key with a key of a virtual keyboarddefined in the scene description, and means intended to activate the keyof the virtual keyboard and to execute a command associated with saidkey, said command being intended to modify a content of the multimediascene.

The present invention is thus adapted to interface a remote controldevice with a multimedia scene by virtue of the creation of a virtualkeyboard in the scene description. With this virtual keyboard and anadapted user interface, a user can interact with the multimedia scene bymeans of a remote control device in a manner which is similar to thatpreviously realized by means of a cursor device.

These and other aspects of the invention are apparent from and will beelucidated, by way of non-limitative example, with reference to theembodiment(s) described hereinafter.

In the drawings:

FIG. 1 illustrates the operation of a video receiver ac

when it communicates with a remote control device; and

FIG. 2 is a block diagram illustrating the method of assigning abehavior to a key of the remote control device.

The present invention relates to the control of multimedia scenes bymeans of a remote control device. In the preferred embodiment, themultimedia scenes are the result of an encoding/decoding operation inaccordance with the MPEG4 standard, but they may alternatively be theresult of an encoding/decoding operation in accordance with a standardwhich is equivalent to the MPEG-4 standard.

FIG. 1 illustrates the operation of a video receiver according to theinvention, said receiver being suitable for receiving a scene defined bya scene description. The video receiver is, for example, a set top boxfor digital television. It is intended to communicate with a remotecontrol device RC provided with keys Bi, i being an integer between 1and n, n being the number of keys of the device RC. The remote controldevice is, for example, an infrared remote control unit which is capableof emitting specific codes.

The video receiver comprises a user interface API intended to associatea key Bi of the remote control device with a key Ri of a virtualkeyboard VK defined in the scene description BD. To this end,transparent rectangles are created in the BIFS scene description, whichrectangles are positioned outside a screen where the multimedia scene MSwill be displayed, or in a zone of the screen with which the user cannotinteract. These transparent rectangles correspond to the keys Ri of thevirtual keyboard, which constitutes a representation of the remotecontrol device in a virtual space. The user interface API comprises, forexample, a memory intended to store a matrix of the positions of thekeys of the virtual keyboard.

Moreover, each key of the virtual keyboard is associated with a specificnode of the BIFS scene description, which is a TouchSensor node. When akey of the remote control device is pressed, the user interface issuitable to convert the pressure on said key into a position of a key ofthe virtual keyboard and to subsequently activate the key of the virtualkeyboard in the BIFS scene description. A particular behavior can beassigned to the key of the virtual keyboard in order to execute acommand intended to modify a content of the scene. This assignment of abehavior is realized by using a mechanism for managing BIFS events whichare known to those skilled in the art. Thanks to the invention, it isthus possible to navigate between the different video sequences within amosaic i

by means of a remote control unit.

FIG. 2 describes the method of assigning a behavior to a key of theremote control device. This method comprises the steps of:

-   -   pressing PRES on a key of the remote control device;    -   identifying ID&TR the key of the remote control device thus        pressed and converting said key into a key of the virtual        keyboard via the user interface;    -   activating ACT the key of the virtual keyboard by way of the        TouchSensor node of the tree describing the BIFS scene; and    -   executing EXE a command associated with the key of the virtual        keyboard by the BIFS event manager.

The BIFS scene must carry out the complete description of the keys ofthe virtual keyboard. An example of a part of a BIFS scene describing akey of the virtual keyboard is given below in the VRML language, withcomments preceded by the sign #.

# Definition of a key ARROW_UP of a virtual keyboard # Transform 2D {translation −50 100 # position of the key in the scene children { DEFARROW_UP TouchSensor { } # this key may be activated Shape # definitionof the geometry of the key { geometry Rectangle {size 2 2} # a square of2 × 2 pixels appearance Appearance { material Material2D { emissiveColor0 0 0 filled FALSE transparency 1 # key not visible } 5 } } } } . . .# Event managementROUTE ARROW_UP.isActive to NODE.activate # if the key ARROW_UP isactivated, a command is executed ...

An example of an implementation in the language C of the user interfaceAPI corresponding to the key ARROW_UP of the virtual keyboard is thefollowing, with comments preceded by the sign //. UserKeyPressed(Bytecode) { struct {int x; Int y; } KEY_LOC; // position variables of thekeys of the virtual keyboard switch ( code) // selection in accordancewith the pressed key of the remote control unit { // list of codes ofthe keys of the remote control unit . . . case UP_KEY_CODE:{KEY_LOC.x=−50; KEY_LOC.y=100; break; } . . . } Double this_time =get_current_media time( ); MouseAt(KEY_LOC.x, KEY_LOC.y, MOUSE_LEFT_(—)BUTTON_DOWN, this time); // function allowing, when a key of the remotecontrol unit is pressed, execution of a command as if a mouse click hadtaken place at the position (x,y). }

It should be noted that any reference sign between parentheses in thepresent text should not be construed as limiting the claims. Use of theverb “comprise” and its conjugations does not exclude the presence ofelements or steps otl

claims. Use of the article “a” or “an” preceding an element or step doesnot exclude the presence of a plurality of such elements or steps.

1. A control system for a multimedia scene defined by a scenedescription, the control system comprising a video receiver suitable forreceiving the multimedia scene, and a remote control device providedwith keys, the video receiver being intended to communicate with theremote control device and comprising: a user interface intended toidentify a key of the remote control device when it is pressed and toassociate said key with a key of a virtual keyboard defined in the scenedescription; means intended to activate the key of the virtual keyboardand to execute a command associated with said key, said command beingintended to modify a content of the multimedia scene.
 2. A videoreceiver suitable for receiving a multimedia scene defined by a scenedescription, said video receiver being intended to communicate with aremote control device provided with keys and comprising: a userinterface intended to identify a key of the remote control device whenit is pressed and to associate said key with a key of a virtual keyboarddefined in the scene description; means intended to activate the key ofthe virtual keyboard and to execute a command associated with said key,said command being intended to modify a content of the multimedia scene.3. A control method, by means of a remote control device provided withkeys, for a multimedia scene defined by a scene description, the scenedescription comprising a virtual keyboard whose keys correspond to keysof the remote control device, said method comprising the steps of:identifying a key of the remote control device when it is pressed;converting said key into a key of the virtual keyboard; activating thekey of the virtual keyboard; and executing a command associated with thekey of the virtual keyboard.